Elastography provides new opportunities in diagnostic imaging for the detection and characterization of disease, particularly cancer, by exploiting the changes in tissue elasticity that occur in nearly all cancerous lesions. The overall goal of this program is to explore methods to generate, interpret, and evaluate elastograms. The program consists of three projects and three cores. Project 1 will be directed by Dr. Bertrand from the University of Montreal. The project aims to develop a computer model of two- and three- dimensional tissue motion to describe the elastographic image formation process. The principal goal is to understand the response of elastic media to an applied stress, and thereby guide data acquisition to obtain accurate strain estimates and minimize artifact-producing distortions. Project 2 will be directed by Dr. Ophir from the University of Texas. The project aims to search for optimal signal processing techniques for elastographic image formation. Image quality factors that determine sensitivity, dynamic range, resolution, contrast, and noise will be investigated in terms of the compromises necessary to maximize task performance. An analysis of image artifacts and methods to minimize or eliminate them will also be investigated. Finally, in vitro studies to measure the elastic properties of normal and pathological breast and prostate tissues will be conducted through a subcontract to Dr. Krouskop at Baylor College of Medicine. Project 3 will be directed by Dr. Insana from the University of Kansas. The project aims to develop objective criteria for evaluating elastographic image quality in terms of low-contrast detectability. A statistical analysis of elastograms will be conducted, and improvements provided by a more complete study of tissue motion (project 1) and better image formation strategies (project 2) will be evaluated by estimating visual detection efficiencies. Core 9001, directed by Dr. Hall from the University of Kansas, will establish and maintain essential communication for data flow between laboratories. Core 9002, also directed by Dr. Hall, will develop and construct sonographic and elastographic phantoms necessary in all three projects. Core 9003, directed by Dr. Ophir, will provide elastographic data and images from phantoms and tissues using the specialized equipment unique to the UT laboratories and clinics. The overall program focus in on the detection and characterization of breast and prostate cancer.